Java servlet singlethreadmodel

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/ 05-Dec-2017 10:33

This means the structure of your WAR module will look something like this: If you don’t package entities in the WEB-INF/classes, then you don’t have to package and the optional in the WAR file. As you can see, packaging the entities with the web module is easy, but you may be wondering how to use them.

There are three common scenarios for using EJB 3 JPA from the web container: ■ Using a container-managed entity manager in a Java EE 5 container ■ Using an application-managed entity manager with a JTA transaction manager in a Java EE 5 container ■ Using an application-managed entity manager with local transactions outside the container The first two cases will be more prevalent because of the power of container-managed entity managers and JTA transactions, but for completeness we’ll discuss all three scenarios in this section.

For instance, you may not want to use JNDI to grab a container-managed Entity Manager instance because you are a fan of dependency injection. You can consider using the @Persistence Unit annotation to inject an instance of an Entity Manager Factory, and then create an application-managed instance of Enti-ty Manager as follows: Just remember that you have to manage the lifecycle of an application-managed Entity Manager (see listing 12.4); the container is not going to do it for you in this situation.

Listing 12.4 Using an application-managed entity manager with a JTA transaction H In listing 12.4 we are doing a lot of housekeeping to manage the lifecycle of the Entity Manager and to manually manage transactions.

Next we’ll discuss how you can use an application-managed Entity Manager with the JTA transaction manager.

That way, you can package the persistence, xml and optional descriptors in the META-INF directory of the JAR.

In this tutorials, it provides many step by step examples and explanations on using Struts 1.x MVC framework. :) Let’s go through a quick start to understand about the Struts 1.x framework.

In Struts validator framework, it provides many generic methods (required, maxlength, minlength..) to validate the form components, it makes your validation code more standardize and easier to maintain.

In this section, we’ll show you how to use entities directly from the web tier.

In topic 11, we explained that entities can be packaged in the web module, but we skipped over the details of how to do it.

For instance, you should avoid dependency injection. If you’re planning to use JPA from a managed class like a servlet, you may be tempted to inject an instance of an Entity Manager by using the @Persistence Con-text annotation like this: If you use this and test your application, it will probably run successfully in your first few attempts.